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=============================================================================
FreeBSD-SA-16:08.bind                                       Security Advisory
                                                          The FreeBSD Project

Topic:          BIND remote denial of service vulnerability

Category:       contrib
Module:         bind
Announced:      2016-01-27
Credits:        ISC
Affects:        FreeBSD 9.x
Corrected:      2016-01-20 08:54:35 UTC (stable/9, 9.3-STABLE)
                2016-01-27 07:42:11 UTC (releng/9.3, 9.3-RELEASE-p35)
CVE Name:       CVE-2015-8704

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

BIND 9 is an implementation of the Domain Name System (DNS) protocols.
The named(8) daemon is an Internet Domain Name Server.

Address Prefixes List (APL RR) is a type of DNS Resource Record defined in
RFC 3123.

II.  Problem Description

There is an off-by-one error in a buffer size check when performing certain
string formatting operations.

III. Impact

Slaves using text-format db files could be vulnerable if receiving a
malformed record in a zone transfer from their master.

Masters using text-format db files could be vulnerable if they accept
a malformed record in a DDNS update message.

Recursive resolvers are potentially vulnerable when debug logging is
enabled and if they are fed a deliberately malformed record by a
malicious server.

A server which has cached a specially constructed record could encounter
this condition while performing 'rndc dumpdb'.

IV.  Workaround

No workaround is available, but hosts not running named(8) are not
vulnerable.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

The named service has to be restarted after the update.  A reboot is
recommended but not required.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

The named service has to be restarted after the update.  A reboot is
recommended but not required.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-16:08/bind.patch
# fetch https://security.FreeBSD.org/patches/SA-16:08/bind.patch.asc
# gpg --verify bind.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable daemons, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r294405
releng/9.3/                                                       r294905
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://kb.isc.org/article/AA-01335>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-8704>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:08.bind.asc>
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